                              (map first))]
     not-found-items))
 
-(defn all-columns [dataset cols]
+(defn all-columns
   "Takes a dataset and any number of integers corresponding to column
   numbers and returns a dataset containing only those columns.
 

      (make-dataset new-columns
                    new-data))))

(defn drop-rows [dataset n]
  "Drops the first n rows from the CSV."
  (map-rows dataset (partial drop n)))

(defn take-rows [dataset n]
  "Drops the first n rows from the CSV."
  (map-rows dataset (partial take n)))

(defn derive-column


(def _ "An alias for the identity function, for providing positional arguments to mapc." identity)

(defn mapc
  "Takes an array or a hashmap of functions and maps each to the key
  column for every row."
  [dataset fs]
  (let [fs-hash (if (vector? fs)
                    (zipmap (column-names dataset) fs)
                    fs)
